Heat transfer unit for heating systems and surefaces and railway  point heater

ABSTRACT

The invention relates to a heat transfer unit ( 1 ) for heating systems and surfaces, which can be connected to at least one geothermal energy probe ( 21 ) as a heat source ( 2 ) operating with a multi-phase working fluid and to a component to be heated, and which comprises at least one heat exchanger ( 11 ) and transport lines ( 12 ) for the gaseous or liquid working fluid. At least one gas-tight heat exchanger ( 11 ) is designed in module form having a plurality of directly adjoining modular mini-channels ( 111 ), depending on the power requirements, in a planar arrangement for transferring the latent heat arising from the heat source ( 2 ) from the heated gaseous portion of the working fluid to the component ( 3 ) to be heated, said mini-channels ( 111 ) being connected to at least one supply channel ( 114, 115 ) and having a diameter of 0.3 to 6 mm. The heat transfer unit ( 1 ) can be integrated into the region of a switch blade ( 32 ) as a railway point heater.

The invention relates to a heat exchanger unit for heating systems andsurfaces, according to the preamble of claim 1, and to a track switchheater having a heat exchanger unit, according to the preamble of claim21.

Document EP 1 529 880 A1 and WO 2005/045134 A1 relate to a thermalground probe which serves heat directly to traffic facilities, the heatflow from which thermal ground probe is conducted via at least one heatpipe from the heat source via a transport zone and, in order to providea supply to a plurality of heat sinks, is split up already in thetransport zone, long before reaching the heat sinks, in such a way thata split takes place in each case from one to two heat flows in order toensure a uniform distribution or a distribution of the heat flowaccording to the respective power demands of the connected heat sinks.The splitting-up of the heat flows from one pipe to two is restricted inthat the sum of the cross sections of the two pipes after thedistribution must be equal to the cross section before the distribution,that is to say the cross section of the pipe which is closer to theprobe is approximately equal in size to the sum of the cross sections ofthe two distribution pipes. Here, the cross sections of the distributionpipes are proportional to the ratio of the power demands of the heatsinks connected downstream.

As a heat exchanger, provision is made in each case of merely a plateunder which the up to three heat pipes are fastened in a heat-conductingfashion longitudinally with respect to the rail body, but are notintegrated. Said pipes are therefore not an independent heat exchanger,but rather are described as being fastened to heat distribution platesin a heat-conducting fashion.

The targeted splitting-up of a gas flow in the transport zone requiresthat the calculated geometrical dimensions of the distribution pipes beadhered to very precisely, and it is not possible for said geometricaldimensions to be realized in assembly under the conditions prevailing atthe track. No weld or solder seams should project into the interiorspace of the pipe, nor should any burrs protrude into said interiorspace, since such seams or burrs hinder the gas flow and the condensateflow. The splitting-up of the large heat flow from the probe into aplurality of relatively small flows by means of a further interposedheat exchanger, as proposed in EP 1 529 880 A1, is associated withtemperature losses, which would not necessarily be advantageous in thecase of the small temperature difference which is present. The referenceto capillary pipes in document EP 1 529 880 A1, which utilize acapillary effect in some arbitrary way, cannot be regarded as beingequivalent to pipes of small diameter at least in connection with theuse of CO₂, since at such small diameters, the pressure drop in the pipewith the length of up to 5 m specified in EP 1 529 880 A1 is so highthat transportation of gas no longer takes place. It is in fact priorart for pipes with a capillary internal structure and diameters of 10 mmto be used to generate a backward flow of condensate in the horizontal,or even counter to a slight gradient up to a length of 5 m. With asmooth internal structure and a diameter which does not generate apressure drop, a backward flow of a condensate is not physicallypossible.

The heating of traffic signs using geothermal heat, as is known from DE40 36 729 A1, requires only very small heat quantities and can berealized in a relatively simple manner. A significant difference withrespect to the invention proposed here is the power ranges, which arehigher here by factors of 20 to several hundred. An increase in power ofthe described method into the range involved here is not possible. Ofequal significance for the lack of comparability is the fact that saiddocument involves the prevention of an obstruction to visibility causedby frost. A further fundamental difference also lies in the fact that,in a traffic sign, only vertical distances must be overcome in thedistribution of heat, and only vertical surfaces need be thawed. Here,gravity performs the significant task of causing the precipitation,snow, sleet or frost only in the thawed state to slide down. The heatedtraffic sign is duly a heat pipe application, but the realization of amulti-duct heat exchanger is designed explicitly for water/glycolmixtures. The proposed design having a so-called heat pipe has only onepipe with a plate, which is fastened thereto and which conducts theheat, as a heat sink.

Already widespread, and known for example from DE 43 25 002 A1, aredevices for heating track switch parts by means of electric heatingelements which are arranged locally and which are intended to ensurethat the track switch can be operated even at low temperatures below thefreezing point.

The object on which the invention is based is that of developing a heatexchanger unit which is adapted to the specific demands of anapplication and, here, constitutes an efficient and economical solution.

The invention is realized with regard to a heat exchanger unit by meansof the features of claim 1, and with regard to a track switch heater bymeans of the features of claim 21. The further dependent claims relateto advantageous embodiments and refinements of the invention.

The invention encompasses the technical teaching with regard to a heatexchanger unit for heating systems and surfaces, which heat exchangerunit can be connected at least to a thermal ground probe, which isoperated with a multi-phase working medium, as a heat source and to acomponent to be heated, and which heat exchanger unit is composed of atleast one heat exchanger and transport lines for the gaseous or liquidworking medium. According to the invention, for the transfer of thelatent heat originating from the heat source from the heated gaseouscomponent of the working medium to the component to be heated, at leastone gas-tight heat exchanger is formed, in a modular fashion, with amultiplicity of directly adjacent, depending on the power requirement,mini-ducts in a laminar arrangement, which mini-ducts are connected toat least one supply duct, and the mini-ducts have a diameter of 0.3 to 6mm.

That diameter of the mini-ducts which is provided as a lower limit isdistinct from the dimensions of micro-ducts, for which the literaturespecifies a diameter of <0.3 mm. In the literature, a dimension of amini-duct is often specified as being in the range between 0.3 mm and 3mm diameter. In the case of relatively large surfaces to be heated, thediameters of the mini-ducts in this context may even be up to 6 mm. Evenat such diameters, the ducts are integrated into the component to beheated; the component to be heated therefore is itself the heatexchanger.

Two variants of heat exchangers are possible, the parallel flowprinciple and the counterflow principle.

For both principles, at a temperature of the working medium of 7° C. inthe heat exchanger, the desired specific power range of the heatexchanger unit lies between 0.4 and 4 kW/m².

To increase the size of the duct surface and therefore of the heattransfer area between the gas and the heat exchanger, it is possible fora plurality of layers of ducts to be arranged one above the other whilemaintaining the minimum spacing of the ducts with respect to one anotherwhich must be adhered to for mechanical reasons (strength). With saidmeasure, it is also possible for an even faster heating response to beobtained.

For the counterflow principle: the ratio of the cross sections of thefeeding distributor pipes to the overall cross section of therespectively connected ducts should be selected to be between 0.1 and0.25 depending on the power requirement of the surface to be heated andthe selected duct cross sections. The sum of the cross sections of themini-ducts is accordingly significantly greater than that of anassociated distributor pipe. The mini-ducts conventionally have a smoothinner wall in order to assist the gas and liquid flow as effectively aspossible.

It is possible to specify a minimum diameter on the capillary side of0.3 mm, and a maximum diameter in the case of aluminum heat exchangers,for reasons of strength and economy (excessively high wall thicknesses),of 5 mm. The minimum diameter therefore also should not be undershot,such that the return flow of the liquid working medium is not hinderedby the inflowing gas. Intermittent behavior of the medium may occur evenwith a diameter of 1 mm and at high power.

On the distributor side, the maximum diameter should not exceed 20 mm.The Product Safety Act sets limits on production monitoring, and demandsfrequent safety checks, for significantly greater diameters. The Actseizes the exceedance of limit values from the product of pressure andvolume of a reservoir. Furthermore, the wall thicknesses then becomeuneconomically thick.

When using CO₂, the dimensions of the distributor pipes and themini-ducts at power levels required for such applications (<2 kW per m²and distributor pipe) are substantially non-critical. The high enthalpycontent of CO₂ entails a low flow speed. A metallic heat exchanger, onaccount of its good thermal conductivity, is effective at dissipatingthe latent heat of the gas, as a result of which a suction effect, so tospeak, is generated which even permits unequal capillary tube crosssections without this leading to critical power losses.

If the power requirements are increased disproportionately in relationto the cross section of the ducts, a build-up of condensate can occur,that is to say the outflowing condensate hinders the inflow of gaseousmedium, such that power-reducing, intermittent behavior of the heattransfer is generated.

For the parallel flow principle, the cross sections of the distributorpipes and ducts can be selected to be smaller.

Modules of 25 W to 200 W have been proposed for use in track switchheaters. The dimensions are coordinated with the type of track switchand the required snow-melting power, and may encompass heating of theslide chairs.

Here, the invention is based on the notion of specifying a heatexchanger unit for utilizing, collecting and distributinglow-temperature heat which preferably originates from a thermal groundprobe, which heat exchanger unit is operated with a liquid-gaseousworking medium. As a suitable heat source, it is preferable to use thelatent heat of a working medium even in the case of an only slighttemperature gradient between the phase change point of the workingmedium and the freezing point of water, with it being possible tomaximize the power which can be transmitted to the heat sink, and tosignificantly improve efficiency.

The heat exchanger is designed such that preferably geothermal heat at alow temperature level is used for heating and temperature control insuch a way that, even with the small temperature differences between theworking medium and the heat sink, such as are present if the temperaturelevel of the working medium is not raised by any interposed heat pump,it is possible for a large quantity of heat to be transferred over alimited area, that is to say a high energy density is obtained.

It can be expected that up to 95% of the heat extracted from the probeis not utilized for melting snow or ice, but rather that considerableheat quantities are dissipated by convection at temperatures below 10°C. and by radiation into the open air.

By means of the invention, therefore, for the control of the extractionof heat from the heat source, a minimization of the uncontrolledextraction of heat is passively obtained by means of the configurationof the surface of the heat exchanger. This is provided by means of theconfiguration of the surface and/or the material selection of the heatexchanger.

It is additionally possible for the flow of the working medium to bereduced or even interrupted by means of temperature-dependentregulation. This is preferably achieved in that, at a position which isprotected from wind and radiation, a temperature-controlled actuatorraises the heat exchanger at one side, or raises the feed pipe by asmall amount, in such a way that the return flow of the medium isinterrupted.

One significant innovation of the invention over known solutions relatesto improvements in the efficiency of the core components, particularlywith regard to the distribution of heat, which improvements may also beused in other applications and even permit effective low-temperatureutilization in said applications for the first time. With the invention,the efficiency of previous known solutions is surpassed with regard topower, material use and economy. Furthermore, additional systemcomponents are proposed, such as for example the integration of heataccumulators and additional heat sources, or an additional integrationof heat accumulators into the heat exchanger itself.

Microstructure heat exchangers differ from other heat exchangers bytheir high power density. It is preferable, depending on the requiredpower and the resulting overall duct cross section which is defined bythe overall duct length and the duct cross section, for 2 toapproximately 100 ducts to be arranged per 10 centimeters width of theexchanger. The heat exchanger operates with only a small temperaturedifference and around the condensation point of the working medium, withthe operating points of the two fluid phases lying close to one of theirphase change points. In particular, the combination of a microstructureheat exchanger according to the invention in connection with theutilization of geothermal heat offers particular advantages, viewed asan overall system, with regard to system integration, operationalreliability and freedom from maintenance.

The heat exchanger unit serves in particular for heating trafficsurfaces, traffic infrastructure and traffic facilities. In thisconnection, the heat exchanger unit is particularly suitable forrailroad equipment, in particular for track switches and also forrailroad crossing segments or platform segments designed as heatexchangers and similar units designed as heat exchangers, since thesolution according to the invention can be operated without additionalpumps driven by external energy and without moving parts. The heatexchangers can be connected, preferably in a releasable andnon-destructive fashion, to in each case one or more supply lines.

For heating traffic facilities, such as railroad track switches, and forthe clearance of snow and ice and therefore applications for increasingsafety in high-risk regions such as platform edges, railroad crossingsor grade crossings, it is therefore possible to dispense with the use offor example electric heating, or the use of gritting means or means forreducing the melting point of the snow.

Furthermore, it is possible to minimize the flow losses and pressurelosses in the heat exchanger resulting from the mutual hindrance of thegas phase and the condensate returning to the heat source.

The particular advantage is that the heat exchanger unit according tothe invention has a level of efficiency, with regard to heatutilization, material use and economy, which surpasses that of thepresent state of the art. The efficiency with regard to the utilizationof heat results from the optimized dissipation of the heat flowing outacross a temperature gradient.

In a preferred embodiment of the invention, the mini-ducts may bearranged, in the case of a particularly high heat requirement, in aplurality of planes. To be able, with the small temperature difference,to transfer a heat quantity which is required for the intended purpose,the heat transfer area on the side of the working medium must bemaximized. Said heat exchanger is formed in one plane, or in a pluralityof planes depending on the energy requirement, of a plurality ofparallel-running ducts, but preferably 2 to 100 ducts per 10 centimetersof width of the heat exchanger and per plane. The duct diameterpreferably lies between 0.5 mm and 5 mm. In this way, the transfer areafrom the working medium to the heat exchanger, and therefore thepossible energy density, is maximized. At the same time, however, thesurface area with respect to the environment must be kept as small aspossible in order to minimize the radiation losses to the environment.In selecting the material of the heat exchanger, it is sought to obtaingood conductivity and a high level of corrosion resistance.

In this way, the heat exchanger may take the form of a microstructureso-called plate-type heat exchanger which, using the micro-channelprinciple, is optimized according to the working medium which is used,preferably CO₂, and the application.

When using CO₂ as a working medium, a configuration of the inflowconditions, as is known in heat exchangers, is only necessary in thecase of extreme power demands, since with simple branching of the ductsfrom the distributor pipe, the temperature difference in the heatexchanger with respect to optimum inflow conditions is only a few tenthsof a degree. The design from FIG. 1 or FIG. 3 is adequate. Flaring ofthe capillary pipes is not necessary with CO₂ even in counterflow heatexchangers if said minimum diameters of the ducts are adhered to and thepower does not exceed an output power of 5 kW/m².

It is advantageously possible, in order to improve the return flow ofthe condensate in counterflow heat exchangers, for the closed “ends” ofthe ducts to be curved upward. In this way, it is achieved that thecondensate from said region is provided with an impetus and improves theoverall return flow. This is advantageous in particular with relativelylong ducts, such as may be provided in platform edge heaters or railroadcrossing heaters.

It is advantageously possible for the upper apex line of a mini-duct torun in both a rising and falling manner in sections proceeding from theinlet point of the gaseous component of the working medium. Thetransport mechanism of the gaseous medium is based on pressure gradientswhich are generated on account of the reduction in the volume of thegaseous working medium as a result of condensation. The guidance of thegaseous medium is basically independent of the spatial guidance of theducts.

In particular, however, it is advantageously possible for the upper apexline of a mini-duct to rise proceeding from the inlet point of thegaseous component of the working medium. In this way, the gaseouscomponent of the working medium in the mini-duct is guided moreeffectively overall.

Furthermore, the lower apex line of a mini-duct or of a duct section mayadvantageously be inclined in the direction of the outlet point of theliquid component of the working medium. This ensures an improved outflowof condensate, since the return flow of the liquid working medium iseffected primarily by gravity. To reliably discharge the condensate, theducts should generally have an inclination in the flow direction whichis sufficient but nevertheless as slight as possible, and a crosssection which is adapted to the fluid being used. As a result of itsvery low viscosity, it is possible for very small inclinations and crosssections to be selected for the fluid CO₂ which is preferably provided.

In a preferred refinement of the invention, a mini-duct may widen alongthe longitudinal axis. This may also take place conically. If a heatexchanger to which the supply of heat takes place via a gaseous workingmedium is installed horizontally or approximately horizontally and useis made predominantly of the stored latent heat, the problem may occurthat, as a result of a small gradient, the return flow of the condensateis only assisted to a small degree and further disruptive influencesmust be eliminated. As one measure for improving the return flow, it isproposed that the heat exchanger be designed such that at least theinflow of the gas into the heat exchanger does not prevent or onlyminimally prevents the return flow of the condensate.

In one preferred embodiment, the feed duct may taper along thelongitudinal axis in the flow direction of the gaseous fluid. This maytake place conically. Such a cross-sectional narrowing makes allowancefor the fact that, as a result of the distribution between theindividual mini-ducts, gaseous working medium is constantly extractedfrom a supply duct in the flow direction.

The discharge duct may advantageously widen along the longitudinal axisL in the flow direction of the fluid. Such a cross-sectional wideningmakes allowance for the fact that liquid working medium is constantlypassing from the individual mini-ducts into the discharge ducts in theflow direction.

It is advantageously possible for the feed duct and discharge duct to beformed on one side of the mini-ducts as a supply duct, or for the feedduct and discharge duct to be arranged spaced apart from one another. Itis possible in this way for the length and efficiency of the feed lineor discharge line paths to be optimized according to the structuralrequirements.

In the case of the design with the ports at different sides, there ispractically no mutual hindrance, since the gas flow runs above theoutflowing condensate in the mini-duct, and not oppositely but rather inthe same direction.

It is also possible for the condensate return flow to be arranged in theprofile of a duct. In this case, the cross-section increases up to theoutlet. The gradient angle of the upper envelope line with respect tothe horizontal is positive over the entire length, that is to say isaligned upward in the flow direction. The angle of the lower envelopeline is negative up to the outlet, that is to say directed downward,following gravity, in the flow direction. In said design, the gradientangle of the section from the outlet to the closed end may be formedwith a different, preferably greater gradient. This has the effect thatthe returning condensate is accelerated and, with the kinetic energywhich is introduced in this way, more easily overcomes any horizontalsections in the profile.

As a result of the arrangement of the outlet and inlet—the outlet issituated in any case lower than the inlet—gas is prevented from escapingwithout having dissipated the latent heat contained therein. At the sametime, the outflowing condensate blocks any possible undesired inflow ofgas at the outlet side. Furthermore, it is obtained by means of saidarrangement that the return may extend back in parallel in a separatepipe, separated from the gas flow, into the probe pipe expediently nofurther than up to the boundary between the transport and heatabsorption zones.

If the entire heat exchanger is installed with a slight inclination,then it should be ensured that the installation inclination and theinclination of the ducts at least do not fully compensate one another,but rather supplement one another to the greatest possible extent.

This is provided in that the individual ducts of the heat exchanger areof slightly conical design, with the design having both ports, the gasinlet and condensate outlet on the same side and having the ports, gasinlet and condensate outlet on different sides, preferably at oppositesides, being different. If both ports are on one side, then the widenedend is situated at the port side, with the gradient angle of thelongitudinal axis of the pipe, measured from the port side, with respectto the horizontal being greater than that of the upper pipe envelopeline but smaller than that of the lower pipe envelope line, which shouldbe less than 0°. If the ports are situated at different sides, then thewidened side of the pipe is situated on the side of the condensateoutlet, wherein the gradient angle of the upper pipe envelope line withrespect to the horizontal, measured from the gas inlet side, should beat least greater than 0°. The gradient of the longitudinal axis withrespect to the horizontal should be negative. The gradient angle neednot remain constant over the length of the ducts, that is to say saidgradient angle may differ within the specified boundary conditions andmay thereby be adapted, for example, to the installation conditions.

In both embodiments, the port for the gas supply is situated higher thanthat of the condensate outlet. In the embodiment with the ports on oneside, the hindrance of the flows is minimized, since the gas flow runsabove the condensate return flow.

In one preferred embodiment of the invention, a layer which inhibits thetransfer of heat may be at least partially arranged between the workingmedium and the outer surface of the heat exchanger. An aluminum heatexchanger may possibly have too high a degree of thermal conductivity,such that under some conditions, the thermal probe dissipates too muchheat. With a thin insulating layer, the thermal conductivity on the pathfrom the fluid to the heat exchanger surface may be reduced by virtuallyany desired order of magnitude. The heat exchanger and also furtherparts of the heat exchanger, such as for example transport lines, may beprovided with a layer which inhibits the transfer of heat, such that theregion in particular below the heat exchanger as viewed in the flowdirection is not heated, and the probe is not subjected to unnecessaryloading.

Furthermore, it may be advantageous for the mini-ducts which aretraversed by the working medium to be formed into a housing, wherein theheat conductance values of the materials of the two assemblies—ductsystem and housing—may differ. Here, the production of the distributionand of the ducts composed of plastic is correspondingly cost-effective.

In one preferred embodiment of the invention, a heat accumulator may beintegrated into at least one transport line for the return flow of theliquid working medium to the heat source and/or in at least one heatexchanger. In this way, ambient heat or heat from solar radiation isstored and introduced into the circuit of the working medium.

In one preferred refinement of the invention, a return transport linemay be arranged from the heat accumulator to the heat exchanger for thegaseous working medium formed as a result of the absorption of heat inthe heat accumulator.

Here, one advantage is the reduction in the extraction of heat from theheat source, or the regeneration of said heat. A further reduction inthe extraction of heat from the thermal ground probe and the improvementof the regeneration of said heat may be obtained in this way. It isthereby provided that, by utilizing ambient heat, and in particular heatfrom solar radiation, the temperature of the working medium at the heatsink is temporarily increased to such an extent that the circulation ofthe working medium and the extraction of heat from the ground areinterrupted for said period of time. As a result of said reduction inthe operating duration of a thermal ground probe as a primary heatsource, it is provided that said thermal ground probe may be designedmore cost-effectively. If sufficient installation space is available,the accumulator may also be formed with silica gel or zeolite asaccumulator material.

In one preferred embodiment, an auxiliary heater may be integrated as afurther heat source. In this way, the heat exchanger unit is designedfor an extreme extraction of heat.

The upper side of a heat exchanger may advantageously be installed so asto be at least slightly inclined with respect to the horizontal. If theheat exchanger is installed in a horizontal or virtually horizontalposition and for the purpose of thawing frozen precipitate, the surfaceshould be designed so as to ensure reliable drainage of the thawedprecipitate. This measure also serves to reduce the undesireddissipation of heat to the environment.

Standing water on the heat exchanger would, on account of its high heatstorage capacity, absorb considerable amounts of power, rendering saidpower useless. In contrast, if water, melted snow or melted ice isprevented from remaining on the surface in any more than a thin film ofmoisture, then thermal power is no longer extracted from the heat sourcefor the further melting or heating of the melt water, but rather only asignificantly lower thermal power is extracted as a result of an airflow or radiation. The surface which is therefore proposed isaccordingly designed such that the snow or sleet which falls thereon isimmediately melted as completely as possible, at least partially melted,and the melt water flows off from the surface as a result of an at leastslight gravitational component, preferably from a slightly oblique planewhich runs parallel to the pipes which conduct the working medium. Forthe use of the heat exchanger in track switch heaters, a material isselected which has good thermal conductivity, preferably a metal with asmooth surface, for example aluminum, which at the same time has verysmall heat dissipation values. By means of said measures, it is providedthat more heat than is necessary for clearing snow and ice is extractedfrom the heat exchanger only by convection, such as a cold air flow, andas a result of the pure radiation losses, for example to the coldenvironment. The radiation and convection losses are however kept to thelowest possible level as a result of the minimization of the heatexchanger surface and the material selection.

In one preferred embodiment of the invention, a thermal ground probewhich is fixedly installed in the ground can be separated in terms ofvibration by means of a permanently elastic connecting element. If aheat exchanger which is used is exposed to vibration and shock loading,for example in transportation equipment, and in particular if theworking medium is gaseous and a high working pressure prevails(approximately 40 bar if CO₂ is used), said heat exchanger must beseparated in terms of vibration from a fixedly installed thermal groundprobe, and here, must withstand said high pressure over a long period oftime. Here, the working pressure may be monitored by means of a pressureor temperature display.

Since it must be possible to carry out maintenance work on the trafficfacilities and traffic surfaces, possibly also in order to replacedamaged parts, it must preferably be provided that the elastic elementcan be dismounted in a non-destructive fashion, such that, for example,the heat exchanger can be separated from the thermal ground probe andreplaced in the event of damage or during maintenance work in thesurroundings of the heat exchanger. Since the heat exchanger is notnecessarily rigidly connected to the surface or equipment to be heated,it is also possible for the elastic fastening of said heat exchanger toform a decoupling in terms of vibration.

If the heat exchanger is not the surface or system to be heated butrather must be fixedly connected thereto, it is proposed, in order toimprove the transfer of heat by means of the use of thermally conductivepastes, that the contact pressure of the heat exchanger against the heatsink be increased by means of a screw connection or that a metallicconnection be provided, for example by soldering.

It is advantageously possible for the component to be heated to itselfbe designed as a heat exchanger. In a further advantageous refinement,the mini-ducts may be formed at least as co-supporting elements of thecomponent to be heated. In the event that the heat exchanger constitutesthe component to be heated, the surface of which cannot be formed frommetal, and the radiation losses are therefore greater than in the caseof a metallic surface, the higher thermal energy requirement must betaken into consideration in the design of the probe. Here, for thispurpose, the metallic pipes are designed at least as co-supportingelements of the heat exchanger.

It is advantageously possible for the heat exchanger with its mini-ductsto be designed such that it can be tilted with respect to the horizontalby means of a control unit. The power losses as a result of radiationand convection can be counteracted by means of a temperature-controlledcircuit. This takes place in that the inclination in the condensatereturn flow, preferably in the counterflow embodiment, can be variedsuch that the condensate can no longer flow back. For this purpose, acontrol element which expands or contracts in the event of a temperaturechange may be arranged on the heat exchanger. In this way, theextraction of energy from the heat source can be controlled in atargeted fashion as a function of the ambient temperature. Thiscounteracts an unnecessary extraction of heat from the heat source.

It is advantageously possible for at least one return transport line tobe raised by means of a control unit, thereby preventing the return flowof condensate. Said control unit may in particular be arranged under thecondensate return line, with the aim of raising the return transportline for example only locally in order to prevent the return flow of thecondensate and to interrupt the gas flow. Here, the heat exchanger neednot necessarily be designed to be tiltable.

In a preferred embodiment of the invention as a track switch heater, atleast one heat exchanger can be integrated at least in a slide chair, inthe locking crib, in the region of the track switch tongue on the railweb and/or on the rail base of the track switch.

The heat exchangers are installed such that, in the simplest case, theylongitudinally cover a so-called tie crib in a width of approximatelythe adjustment travel of the track switch tongue, and so as to lieapproximately over half of the width of the inner rail base. If the heatexchanger is additionally used for heating the adjacent slide chairs,then a sufficient transfer of heat of the required heat quantity perunit time is ensured by means of a sufficient contact pressure againstthe slide chairs.

The ties of a track change their position over time after being laid asa result of the occurring load collective. Here, the movements in thelongitudinal direction are of particular significance for the use ofheat exchangers, because as a result of said movements, the installationspace of the heat exchanger changes.

It is advantageously possible for at least one heat exchanger to beintegrated in a slide chair of the track switch. The solution accordingto the invention makes it possible for a slide chair of a track switchto be heated and also for the rail head to be heated. If it is necessaryfor two or more heat exchangers which are supplied with working mediumfrom one heat source to be connected in series, the connection mustcomprise an elastic element in order that opposing movements arecompensated and do not lead to the destruction of the heat exchanger.

A preload is often generated by means of a resiliently mountedconnection. The preload is selected such that a sufficient contactpressure against the respectively delimiting slide chairs is generatedin all positions between the minimum and maximum change in position ofthe ties.

For heating a slide chair in track switches, it is important for saidslide chair to be connected in a heat-conducting fashion to a heatexchanger. Alternatively, in particular where the demands on heatingpower are relatively high, slide chairs are proposed into which a heatexchanger is integrated. Said heat exchanger may be designed as aremovable plate, or the mini-ducts are guided in grooves, which are forexample milled or forged, under or on the slide chair. It is alsopossible for the slide chair and heat exchanger to be formed as onecomponent.

It is advantageously possible for at least one heat exchanger to bearranged in the region of the track switch tongue on the rail web and/oron the rail foot.

To prevent the track switch tongue from possibly becoming fixedly frozento the stock rail, it is proposed that heating be provided by means ofthe corresponding heat exchanger with guidance on the rail web and ductswhich run in the transverse direction with respect to the rail. Thefastening of the heat exchanger and the increase in the contact pressureby means of screws, is preferably done with a bore through the neutralaxis of the rail web. In the case of increased heat requirements, anadditional heat exchanger may be arranged on the outer channel of therail profile below the rail head.

With powers of approximately 120 W per side and crib interval, adequatemelting power is provided even for snowfall of more than 10 cm/h. It isto be assumed that up to 95% of the power output does not take the formof melting power but rather results from radiation and convection. Aminimization of the power which is not utilized for melting is thereforeexpedient and economical.

Likewise, to prevent radiation and convection there, the web and thebase of the stock rail may be thermally insulated to the outside, andthe web may also be thermally insulated to the inside if the structureof the track switch permits this. The insulation may be fastened to therail base and, on the outer side, surrounds the additional heatexchanger which may be provided in the outer channel of the railprofile.

Heat exchangers which are not intended to heat the slide chair or therail head are fastened with clamps to the rail base and lie against theties. Said heat exchangers may also additionally be fastened to a tie.Said heat exchangers are designed in terms of their dimensions suchthat, in the one extreme case, an increase in the tie interval, the heatexchangers do not fall between the ties, and in the other extreme case,a reduction in the tie interval, the heat exchangers are not damaged bythe slide chairs. It is advantageously possible for at least one heatexchanger to also be integrated in the locking crib of the track switchand/or designed as a cover of the locking crib.

In a further preferred embodiment of the invention as a track switchheater, the heat exchanger unit may be mounted on the support points onthe track switch by means of deformable elements. If the heat exchangersare used in railroad engineering for heating track switches in order toclear the latter of snow and ice, then the proposed technology must beadapted to the more difficult requirements. The heat exchangers mustthus be designed such that a change in length of the installation spacedoes not have an influence on function and operational reliability, anddoes not lead to the destruction of the heat exchanger.

If the heat exchanger is designed such that it is a component which ismounted in each case on a tie and covers and heats approximately half ofa tie crib at both sides of said tie, the expenditure for vibrationdecoupling and for the compensation of length variations of theinstallation space to the next heat exchanger can be minimized.

The device according to the invention for the improved utilization ofgeothermal heat for heating systems at low temperature comprises atleast one of the following improvements, such that a heat exchanger isspecified which can be used for temperature control or for heatingpurposes, preferably for heating transportation equipment. In relationto the prior art, said device constitutes a more efficient and moreeconomical method.

In contrast to the known heat exchangers which utilize geothermal heatand which are used in combination with heat pumps and in which the heatis transferred in a controlled fashion from a positively-driven mediumto a second positively-driven medium, it is preferably proposed herethat the latent heat contained in a working medium be dissipateddirectly to the environment.

If the heat transfer area on the side of the working medium ismaximized, then it is possible for the required heat quantity to betransferred even at the low temperature difference from thermal groundprobes.

In this way, the transfer surface area from the working medium to theheat exchanger, and therefore the possible energy density, is maximized.At the same time, however, the surface with respect to the environmentis kept as small as possible as a result of a compact design, so as tominimize the radiation losses to the environment.

The reduction in the extraction of heat from a thermal ground probe, ashas hitherto been realized by means of regulating or actuating elementssuch as valves, takes place in a passive fashion in the solutionaccording to the invention, specifically in that a minimization of theheat extraction to that which is required is obtained by means of thematerial selection and the configuration of the surface of the heatexchanger.

Exemplary embodiments of the invention will be explained in more detailon the basis of schematic drawings, in which, in each caseschematically:

FIG. 1 shows a plan view of a heat exchanger having duct structures andthe flow characteristic of the working medium,

FIG. 2 shows a cross section through a heat exchanger according to FIG.1 along a mini-duct,

FIG. 3 shows a cross section through a further embodiment of a heatexchanger according to FIG. 1 along a mini-duct,

FIG. 4 shows a plan view of a further embodiment of a heat exchangerhaving duct structures and the flow characteristic of the workingmedium,

FIG. 5 shows a cross section through the heat exchanger according toFIG. 4 along a mini-duct,

FIG. 6 shows a plan view of a further embodiment of a heat exchangerhaving duct structures and the flow characteristic of the workingmedium,

FIG. 7 shows a cross section through the heat exchanger according toFIG. 6 along a mini-duct,

FIG. 8 shows a detailed view of the constituent parts of a heatexchanger for forming mini-ducts,

FIG. 9 shows a cross section, running perpendicular to the mini-ducts,of the heat exchanger formed from the constituent parts in FIG. 8,

FIG. 10 shows a partial view of a tie interval heater having transportlines leading from a thermal ground probe,

FIG. 11 shows a partial view of a tie interval heater having an elasticconnecting element for pressure monitoring, and branching transportlines,

FIG. 12 shows a partial view of the tie interval heater having anelastic connecting element for pressure monitoring, and branchingtransport lines, as per FIG. 11 at a different pressure,

FIG. 13 shows a partial view of a further embodiment of a slide chairheater having duct structures,

FIG. 14 shows a partial view of a slide chair heater having a heatexchanger with duct structures additionally integrated in the slidechair,

FIG. 15 shows a cross section through the slide chair heater accordingto FIG. 14, perpendicular to the mini-ducts,

FIG. 16 shows a partial view of a slide chair heater having two heatexchangers which are supplied from one heat source and which have ductstructures and branching transport lines and deformable elements,

FIG. 17 shows a partial view of a slide chair heater which is of complexdesign with a plurality of heat exchangers,

FIG. 18 shows a plan view of the duct guidance in a heat accumulator,

FIG. 19 shows an arrangement of the individual system elements with aheat exchanger and heat accumulator of a heat exchanger unit,

FIG. 20 shows an arrangement of the individual system elements with aheat exchanger and heat accumulator of a heat exchanger unit inconnection with a thermal ground probe,

FIG. 21 shows a partial view of a locking crib heater having ductstructures,

FIG. 22 shows a partial view of a further embodiment of a locking cribheater having duct structures,

FIG. 23 shows a cross section through a heat exchanger along a mini-ductwhich operates on the counterflow principle,

FIG. 24 shows a cross section through a heat exchanger along a mini-ductwhich operates on the counterflow principle, in the working position,

FIG. 25 shows a cross section through a heat exchanger along a mini-ductwhich operates on the counterflow principle, in the standby position.

Corresponding parts are denoted by the same reference symbols in all thefigures.

FIG. 1 shows a plan view of a heat exchanger 11 having duct structures111, 114, 115 and the flow characteristic FG, FF of the working medium.

The heat exchanger 11 has, in the transverse direction, a multiplicityof mini-ducts 111 which run parallel to one another. The gas inflow andthe condensate return flow of the working medium take place in directlyadjacent feed ducts 114 and discharge ducts 115 which are situated onone side of the mini-ducts 111.

Arrows denoted by FG indicate the flow direction of the gaseous medium.Arrows denoted by FF indicate the flow direction of the liquid mediumafter having dissipated heat in the heat exchanger 11.

In the heat exchanger 11, the parallel mini-ducts 111 may of course alsorun obliquely or may for example be curved in an S-shape or run in aspiral fashion.

FIG. 2 shows a cross section through a heat exchanger 11 according toFIG. 1 along a mini-duct 111. The gas inflow and the condensate returnflow of the working medium take place in directly adjacent feed ducts114 and discharge ducts 115 which are situated on one side of themini-ducts 111. In this case, the mini-ducts are formed with a constantcross section along the longitudinal axis L. Such mini-duct arrangementsare preferably installed with a longitudinal axis L which is inclinedslightly with respect to the horizontal, so as primarily to ensure thecondensate return flow and thereby improve the power.

FIG. 3 shows a cross section through a further embodiment of a heatexchanger 11 according to FIG. 1 along a mini-duct 111. In this case,the upper apex line OS of the mini-duct 111 rises slightly proceedingfrom the feed duct 114 for conducting the gaseous component of theworking medium. The lower apex line US is inclined in the direction ofthe discharge duct 115 for discharging the liquid component of theworking medium. In this case, the normally preferred inclination of thelongitudinal axis L of the mini-ducts 111 is already integrated in theheat exchanger 11 itself.

FIG. 4 shows a plan view of a further embodiment of a heat exchanger 11having duct structures 111, 114, 115 and the flow characteristic FG, FFof the working medium.

The associated cross section through the heat exchanger 11 according toFIG. 4 along a mini-duct 111 is shown in FIG. 5. In said embodiment, thefeed duct 114 and the discharge duct 115 are situated in each case onopposite sides of the mini-ducts 111. The profile of a mini-duct 111again has an upper apex line OS which rises continuously from the inletpoint 112 of the gaseous component of the working medium. The lower apexline US, in contrast, is inclined in the direction of the outlet point113 of the liquid component of the working medium.

FIG. 6 shows a plan view of a further embodiment of a heat exchanger 11having duct structures 111, 114, 115 and the flow characteristic FG, FFof the working medium. In said embodiment, the discharge duct 115divides the mini-ducts 111, which run parallel to one another, into twohalves.

FIG. 7 shows a cross section through the heat exchanger 11 according toFIG. 6 along a mini-duct 111. Here, the upper apex line OS of themini-duct 111 rises continuously from the feed duct 114 for conductingthe gaseous component of the working medium. The lower apex line US isinclined, in its partial sections, in each case in the direction of thedischarge duct 115 for discharging the liquid component of the workingmedium.

FIG. 8 shows a detailed view of the constituent parts of a heatexchanger 11 for forming mini-ducts 111. The heat exchanger 11 iscomposed of an upper shell 116 and a lower shell 117, between which apunched corrugated plate 118 is arranged to form the mini-ducts 111. Theheat exchanger, formed from an upper shell 116, lower shell 117 andcorrugated plate 118, may also be produced in one piece from an extrudedprofile.

The described multi-part configuration of the heat exchanger 11 may alsobe utilized in the application such that, for example, the upper shell116 or lower shell 117 individually may be integrally connected to thecomponent to be heated. In this case, the final assembly of the heatexchanger 11 is then carried out on site. The described single-piececonfiguration serves to ensure a minimum heat transfer resistance fromthe heat exchanger to the component to be heated.

FIG. 9 shows a cross section, running perpendicular to the mini-ducts111, of the heat exchanger 111 formed from the constituent parts in FIG.8. Here, the upper shell 116 and the lower shell 117 are joined togetherwith the corrugated plate 118. The corrugated plate 118 is connected tothe upper shell 116 and lower shell 117 in a pressure-tight manner andis in good thermally conductive contact with the housing formed from thelower shell 117 and upper shell 116.

FIG. 10 shows a partial view of a tie crib heater having a thermalground probe 21 and transport lines 12. In FIG. 10A, the transport lines12 are guided along the side surfaces of the tie 37 to the rail 38. InFIG. 10B, the transport lines 12 are arranged along one side surface ofthe tie 37.

FIGS. 11 A and B show a partial view of a tie crib heater having anelastic connecting element 14 for pressure monitoring, and branchingtransport lines 12. The transport lines 12 are guided partially over theouter region of the tie 37 and, in the further profile, toward the sidesurface and under the rail 38. The connecting element 14 is designed asan integrated pressure display which signals a possible pressure drop inthe system, which manifests itself in a change in length of the elasticconnecting element 14. FIGS. 12 A and B show a partial view of a furtherembodiment of the tie crib heater having an elastic connecting element14 for pressure monitoring, and branching transport lines 12 which arearranged on one side surface of the tie 37.

The functional reliability of the heat exchanger, which is dependent onthe operating pressure being adhered to, is monitored by means of apressure display which is integrated into the elastic element of thevibration isolation arrangement. Said elastic element is a corrugatedpipe which is arranged in the transport zone so as to be visibleadjacent to the end of the tie. If the operating pressure in the pipe isadequate, the corrugated pipe is extended; if the operating pressurefalls as a result of damage, then the corrugated pipe is shortened. Thedamage is therefore evident from viewing the corrugated pipe, or thedamage is signaled by means of an electrical contact which is triggeredwhen the corrugated pipe is shortened. A comparison of FIGS. 11 A and Band of FIGS. 12 A and B shows the effect of the pressure-dependentchange in length, which is indicated by the elastic connecting element14. The pressure display may also be provided by virtue, for example, ofa pressurized supply pipe being composed of elastic material, which sagsin the event of a significant pressure drop.

FIG. 13 shows a partial view of a further embodiment of a track switchand slide chair heater having duct structures 111, 114, 115. The heatingtakes place by means of outer ducts 111 which are guided around theslide chair 31 and which are arranged on the tie 37. The individualducts 111 may also have different cross sections in order to provide auniform distribution of the gaseous working medium. The heat exchanger11 runs parallel to the rail 38 so as to also heat the latter in partialsections.

FIG. 14 shows a partial view of a track switch and slide chair heateradditionally having a heat exchanger 11 with duct structures 111integrated in the slide chair. The heat exchanger 11 again runs parallelto the rail 38 so as to also heat the latter in sections. The slidechair 31 has, at the top in the center on the tie 37, a sufficientcutout into which are formed additional grooves for holding mini-ducts111.

As can be seen from FIG. 15 in a cross section through the slide chairheater according to FIG. 14 perpendicular to the mini-ducts, anadditional plate is placed as an upper shell 116 into the cutout, whichupper shell 116 absorbs the pressure forces originating from the trackswitch tongue. The slide chair 31 is itself designed, in effect, as aheat exchanger 11.

FIG. 16 shows a partial view of a track switch and slide chair heaterhaving two heat exchangers 11, which are supplied from one heat source,with duct structures 111, 114, 115 and branching transport lines 12. Thearrangement of two heat exchangers, which are fed from one probe pipe,with longitudinally running ducts also has a deformable element 36 onthe slide chair 31 for length compensation of the installation space inthe tie interval. The transport line 12 has a slightly bulged shape atthe base side for the improved separation of the gas phase and of thecondensate by the lower condensate duct.

FIG. 17 shows a partial view of a track switch and slide chair heaterwhich is of complex design and has a plurality of heat exchangers 11fastened to the tie or to the slide chair. The figure illustrates ajuxtaposed arrangement of heat exchangers 11 with mini-ducts runninglongitudinally with respect to the rail 38. Said mini-ducts may also bearranged transversely with respect to the rail. The ties of a rail andthe slide chairs change their positions over time after having been laidon account of the occurring load collective. Therefore, in each case twoheat exchangers 11 are arranged in pairs on one slide chair 31, with acertain gap remaining between the two heat exchangers 11 for lengthexpansion. The working medium is supplied from a probe pipe (notillustrated in the figure) to the heat exchangers 11 which are arrangedin series, with the heat exchangers 11 being supplied from branchingtransport lines 12. In this case, the feed and return transport linesare realized by one pipe.

FIG. 18 shows a plan view of the duct guidance in a heat accumulator 13.Here, said heat accumulator 13 is for example a latent heat accumulatorfrom which the condensate flowing back from the heat sink absorbs theheat contained in the heat accumulator, evaporates and flows to the heatsink—the heat exchanger 11—again without heat having to be extractedfrom the thermal ground probe as a source. In the lower-lying sectionplane A, one possible arrangement of zones of accumulator material whichrun parallel to one another is illustrated.

In order that the return-flowing gas and the condensate running in theopposite direction influence one another only to a small extent, theducts are widened in the direction of the gas flow, preferablyhorizontally. The ducts preferably have, corresponding to the heat whichcan be absorbed in the heat source, a plurality of outlets situated inthe profile of the condensate flow, through which outlets the gasescapes from the duct and flows back to the heat exchanger. The heataccumulator 13 may be split into a plurality of regions. Therefore, theheat in the respective region is extracted parallel thereto. If the heatsource is cooled in the first section, then the condensate here is nolonger evaporated, but rather passes into the second region, absorbs theheat from said second region, evaporates and flows back through the nextoutlet to the heat sink. The processes are similar in the furtherregions. The separation into a plurality of regions has the advantagethat the gas does not flow in the opposite direction to the condensateover the entire pipe length in the heat source, and the two phases thushinder one another only to a small extent.

FIG. 19 shows an arrangement of the individual system elements with aheat exchanger 11 and heat accumulator 13 of a heat exchanger unit. Thearrangement of the system elements has the connection of the heatexchanger 11 and of the heat accumulator 13 via the transport lines 14with elastic connecting elements 14. The flow directions of the workingmedium through the system are also shown.

FIG. 20 shows the arrangement of the individual system elements with aheat exchanger 11 and heat accumulator 13 of a heat exchanger unit 1 inconnection with a thermal ground probe 21 as a heat source 2. Forillustration, the flow directions of the working medium through thesystem are again shown.

FIGS. 21 and 22 show an arrangement of the heat exchanger 11 for alocking crib heater of a track switch 3. The locking crib 35 is coveredby a heat exchanger 11 so as to minimize the infiltration of snow orice. A further heat exchanger which prevents freezing of the melt watermay be arranged on the base of the locking crib, and the water may bedischarged in this way.

FIG. 23 shows a cross section through a heat exchanger 11 along amini-duct 111 which operates on the counterflow principle. To improvethe return flow of the condensate in a virtually horizontally arrangedheat exchanger, the closed end is turned upward in the counterflowembodiment. The feed 114 and discharge 115 ducts are formed in one as aunitary supply duct.

FIGS. 24 and 25 show a cross section through a heat exchanger 11, havinga tilting mechanism 4, along a mini-duct 111 which operates on thecounterflow principle. In FIG. 24, the duct is tilted in the workingposition. On account of the inclination in said position, the liquidworking medium can flow out to the heat source unhindered. In contrast,in FIG. 25, the heat exchanger 11 is in a standby position. Themini-ducts 111 of the heat exchanger 11 are inclined by the tiltingmechanism in such a way that the condensed working medium can no longerflow back to the heat source. The extraction of energy from the heatsource can be controlled in a targeted fashion in this way.

LIST OF REFERENCE SYMBOLS

-   1 Heat exchanger unit-   11 Heat exchanger-   111 Mini-ducts-   112 Inlet point-   113 Outlet point-   114 Feed duct, supply duct-   115 Discharge duct, supply duct-   116 Upper shell-   117 Lower shell-   118 Corrugated plate-   12 Transport lines-   121 Feed transport line-   122 Return transport line-   13 Heat accumulator-   14 Connecting element-   2 Heat source-   21 Thermal ground probe-   22 Auxiliary heater-   3 Component to be heated; track switch-   31 Slide chair-   32 Track switch tongue-   33 Rail web-   34 Rail base-   35 locking crib-   36 Deformable elements-   37 Tie-   38 Rail-   4 Tilting mechanism, control unit-   OS Upper apex line of a mini-duct-   US Lower apex line of a mini-duct-   L Longitudinal axis of a mini-duct-   FG Flow direction of gaseous medium-   FF Flow direction of liquid medium-   A Lower section plane

1. A heat exchanger unit (1) for heating systems and surfaces, whichheat exchanger unit (1) can be connected at least to a thermal groundprobe (21), which is operated with a multi-phase working medium, as aheat source (2) and to a component (3) to be heated, and which heatexchanger unit (1) is composed of at least one heat exchanger (11) andtransport lines (12) for the gaseous or liquid working medium,characterized in that, for the transfer of the latent heat originatingfrom the heat source (2) from the heated gaseous component of theworking medium to the component (3) to be heated, at least one gas-tightheat exchanger (11) is formed, in a modular fashion, with a multiplicityof directly adjacent mini-ducts (111) in a laminar arrangement, whichmini-ducts (111) are connected to at least one supply duct (114, 115),and in that the mini-ducts (111) have a diameter of 0.3 to 6 mm.
 2. Theheat exchanger unit as claimed in claim 1, characterized in that themini-ducts (111) are arranged in a plurality of planes in the heatexchanger (11).
 3. The heat exchanger unit as claimed in claim 1,characterized in that the upper apex line (OS) of a mini-duct (111) runsin both a rising and falling manner in sections proceeding from theinlet point (112) of the gaseous component of the working medium.
 4. Theheat exchanger unit as claimed in claim 1, characterized in that theupper apex line (OS) of a mini-duct (111) rises proceeding from theinlet point (112) of the gaseous component of the working medium.
 5. Theheat exchanger unit as claimed in claim 1, characterized in that thelower apex line (US) of a mini-duct (111) or of a duct section isinclined in the direction of the outlet point (113) of the liquidcomponent of the working medium.
 6. The heat exchanger unit as claimedin claim 1, characterized in that a mini-duct (111) widens along thelongitudinal axis (L).
 7. The heat exchanger unit as claimed in claim 1,characterized in that the feed duct (114) tapers along the longitudinalaxis (L) in the flow direction of the gaseous fluid.
 8. The heatexchanger unit as claimed in claim 1, characterized in that thedischarge duct (115) widens along the longitudinal axis (L) in the flowdirection of the fluid.
 9. The heat exchanger unit as claimed in claim1, characterized in that the feed duct (114) and discharge duct (115)are formed on one side of the mini-ducts (111) as a supply duct, or thefeed duct (114) and discharge duct (115) are arranged spaced apart fromone another.
 10. The heat exchanger unit as claimed in claim 1,characterized in that a layer which inhibits the transfer of heat is atleast partially arranged between the working medium and the outersurface of the heat exchanger (11).
 11. The heat exchanger unit asclaimed in claim 1, characterized in that the mini-ducts (111) which aretraversed by the working medium are formed into a housing, wherein theheat conductance values of the materials of the assemblies may differ.12. The heat exchanger unit as claimed in claim 1, characterized in thata heat accumulator (13) is integrated into at least one transport line(12) for the return flow of the liquid working medium to the heat source(2) and/or in at least one heat exchanger (11).
 13. The heat exchangerunit as claimed in claim 12, characterized in that a return transportline (122) is arranged from the heat accumulator (13) to the heatexchanger (11) for the gaseous working medium formed as a result of theabsorption of heat in the heat accumulator (13).
 14. The heat exchangerunit as claimed in claim 1, characterized in that an auxiliary heater(22) is integrated as a further heat source (2).
 15. The heat exchangerunit as claimed in claim 1, characterized in that the upper side of aheat exchanger (11) can be installed so as to be at least slightlyinclined with respect to the horizontal.
 16. The heat exchanger unit asclaimed in claim 1, characterized in that a thermal ground probe (21)which is fixedly installed in the ground can be separated in terms ofvibration by means of a permanently elastic connecting element (14). 17.The heat exchanger unit as claimed in claim 1, characterized in that thecomponent to be heated is designed as a heat exchanger (11).
 18. Theheat exchanger unit as claimed in claim 1, characterized in that themini-ducts (111) are formed at least as co-supporting elements of thecomponent to be heated.
 19. The heat exchanger unit as claimed in claim1, characterized in that the heat exchanger (11) with its mini-ducts(111) is designed such that it can be tilted with respect to thehorizontal by means of a control unit (4).
 20. The heat exchanger unitas claimed in claim 1, characterized in that at least one returntransport line (122) is raised by means of a control unit (4), therebypreventing the return flow of condensate.
 21. A track switch heaterhaving a heat exchanger unit (1) as claimed in claim 1, characterized inthat at least one heat exchanger (11) is integrated at least in a slidechair (31), in the locking crib (35), in the region of the track switchtongue (32) on the rail web (33) and/or on the rail base (34) of thetrack switch.
 22. The track switch heater having a heat exchanger unit(1) as claimed in claim 21, characterized in that the heat exchangerunit (1) is mounted on the support points on the track switch (3) bymeans of deformable elements (36).